tests: Trim .nim files trailing whitespace

via OSX: find . -name '*.nim' -exec sed -i '' -E 's/[[:space:]]+$//' {} +

tests/types/tinheritref.nim

@@ -21,7 +21,7 @@ type
   TTreeIterator* [T,D] = ref object {.inheritable.}
 
   TKeysIterator* [T,D] = ref object of TTreeIterator[T,D]  #this not
-  
+
 var
   it: TKeysIterator[int, string] = nil